Radiography is the process of creating images by means of using radiation other than visible light. Perhaps the most well-known example is that of X-rays whereby ionising radiation is passed over an object to produce an image on a radiosensitive surface which can be used e.g. in healthcare, industry and testing, airport security systems and so on.
FIG. 1 shows a conventional digital X-ray system 1. It comprises a radiation source of X-ray photons 3, a scintillator 5, an amorphous silicon panel (ASP) 7, and read-out electronics 9. The scintillator 5 is formed of a material that emits visible light in response to X-ray absorption; it is usually in the form of a flat panel. The light is detected using the ASP 7 which is a relatively complex, expensive and bulky array of photodiodes or thin-film transistors (TFTs) that convert the light into electrical signals which are then interpreted and converted into data by the read-out electronics 9 to represent a two-dimensional image form.
Such a conventional digital X-ray system 1 has a high cost, which is dependent on size, not least because of the expense of the ASP 7 required. In addition, the useful life of such a conventional digital X-ray system 1 is limited because the light sensing elements (photodiodes or TFTs) of the ASP 7 are in practise exposed to radiation which damages the semiconductor material. Such a conventional digital X-ray system 1 is also susceptible to ‘ghosting’ which occurs when X-ray photons causes electrical charge effectively to be trapped in the semiconductor material resulting in previous images (or parts thereof) to appear in new and/or subsequent images. The spatial resolution offered by such a conventional digital X-ray system 1 is also limited by the pixel count, which results from the number of photodiodes and/or TFTS in the ASP 7 which cannot be varied once manufactured.
Additionally, such systems tend to have limited image readout speeds, meaning that the object or patient being imaged would have to be subjected to radiation for longer periods of time, increasing the dose received.